Ensure that Collections.isEmpty() is used to check if there are no
elements in a collections. This is more explicit and can be faster than
calling .size().
Closes gh-4783
Undertow’s WebSocket client sends an illegal Origin header – it does
not include the scheme, e.g. it’ll send “localhost” rather than
“http://localhost”. This commit works around the problem by allowing
access to the SockJS endpoints from any origin, thereby disabling
OriginHandlerInterceptor’s checking of the Origin header.
